Examine source code of Email Tracking Shield

{
  "manifest_version": 3,
  "name": "__MSG_extensionName__",
  "version": "1.0",
  "description": "__MSG_extensionDescription__",
  "icons": {
    "128": "icons/icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{323e4567-e29b-12d3-a556-226614176000}"
    }
  },
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "storage",
    "activeTab"
  ],
  "host_permissions": [
    "*://mail.google.com/*",
    "*://outlook.live.com/*",
    "*://*.yahoo.com/*",
    "*://mail.protonmail.com/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "action": {
    "default_popup": "popup/popup.html",
    "default_icon": {
      "128": "icons/icon128.png"
    }
  }
}